I don't know any of my extended family beyond my parents and sibblings. It makes me a little sad and jealous when I look around at other's large extended families to know that I don't have that, but it is what it is. I never knew exactly why my parents kept themselves isolated from their families; I just assumed there must have been some kind of falling out years ago.
My brother's wife has a very large, and very close, extended family. She recently tracked down my father's brother, my uncle. He was happy to hear some word about his astranged brother and is open to reconnecting with us kids.
I think I need to at least attempt this connection, but terrified to begin. What do I say? "Hi. I'm sorry your brother, my father, was a complete and utter douchebag his entire life. What have you been up to for the last 30 years?"